Radiation synovectomy produces functional ablation of inflamed synovium following intra-articular administration of short range, beta-emitting radio-isotopes. The isotope is complexed to a particular carrier in order to delay and decrease leakage from the joint and thereby reduce the total body radiation exposure. The overall objective of this protocol is to improve the clinical utility of radiation synovectomy in the treatment of rheumatoid synovitis and develop appropriate means to assess the effect of treatment.